This section is intended to introduce various aspects of the art, which may be associated with exemplary embodiments of the present invention. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present invention. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of prior art.
Many enhanced hydrocarbon recovery operations can be classified as one of the following types: pressure maintenance and miscible flooding. In a pressure maintenance operation, inert gasses such as nitrogen are injected into a primarily gaseous reservoir to maintain at least a minimal pressure in the reservoir to prevent retrograde condensation and improve total recovery. In a miscible flooding operation, miscible gasses such as carbon dioxide are injected into a primarily liquidous reservoir to mix with the liquids, lowering their viscosity and increasing pressure to improve the recovery rate.
Many oil producing countries are experiencing strong domestic growth in power demand and have an interest in enhanced oil recovery (EOR) to improve oil recovery from their reservoirs. Two common EOR techniques include nitrogen (N2) injection for reservoir pressure maintenance and carbon dioxide (CO2) injection for miscible flooding for EOR. There is also a global concern regarding green house gas (GHG) emissions. This concern combined with the implementation of cap-and-trade or carbon tax policies in many countries make reducing CO2 emissions a priority for these and other countries as well as the companies that operate hydrocarbon production systems therein. Efficiently producing hydrocarbons while reducing GHG emissions is one of the world's toughest energy challenges.
Some approaches to lower CO2 emissions include fuel de-carbonization or post-combustion capture. However, both of these solutions are expensive and reduce power generation efficiency, resulting in lower power production, increased fuel demand and increased cost of electricity to meet domestic power demand. Another approach is an oxyfuel gas turbine in a combined cycle (e.g. where exhaust heat from the gas turbine Brayton cycle is captured to make steam and produce additional power in a Rankin cycle). However, there are no commercially available gas turbines that can operate in such a cycle and the power required to produce high purity oxygen significantly reduces the overall efficiency of the process.
One proposed approach utilizes an autothermal reformer unit (ATR) to produce hydrogen fuel and carbon dioxide for capture and/or injection. Such systems are disclosed in many publications, including, for example International Patent Application Number WO2008/074980 (the '980 application) and Ertesvåg, Ivar S., et al., “Exergy Analysis of a Gas-Turbine Combined-Cycle Power Plant With Precombustion CO2 Capture,” Elsivier (2004) (the Ertesvag reference), the relevant portions of which are hereby incorporated by reference. The '980 application and Ertesvag references disclose systems for reforming natural gas in an auto-thermal reformer (ATR) to form a syngas, then separating the CO2 from the syngas and sending the hydrogen-rich fuel to a conventional combined-cycle (CC) process.
As such, there is still a substantial need for a low emission, high efficiency hydrocarbon recovery process.